(1) In a LAN, a subnetwork made up of a group of clients and servers under the control of one security database. Dividing LANs into domains improves performance and security.

(2) In a communications network, all resources under the control of a single computer system.

(3) On the Internet, a registration category. See domain name and Internet domain name.

(4) In database management, all possible values contained in a particular field for every record in the file.

(5) A group of end points (phones or gateways) in a SIP telephony environment. See SIP.

(6) In magnetic storage devices, a group of molecules that makes up one bit.

(7) In a hierarchy, a named group that has control over the groups under it, which may be domains themselves.